An awesome and classic card. It can be extremely dangerous, but the catch is that there needs to be something good on the battlefield first. Copying creatures like say...Sublime Archangel can easily turn things in your favor.

4 mana to play something that might've cost MORE than 4 mana. And reap all of the benefits of ETB effects. And shroud/hexproof can't say anything about it. And the legend rule change letting you copy THEIR legendary creature rather than a suicide charge (when in doubt, Unsummon ).